Problem: 2 binders cost $3.46. Which equation would help determine the cost of 14 binders?
Answer: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 2 binders. We want to know the cost of 14 binders. We can write the numbers of binders as a proportion: $\dfrac{2}{14}$ We know 2 binders costs $3.46. We can let $x$ represent the unknown cost of 14 binders. The proportion of these costs can be expressed as: $\dfrac{\$3.46}{x}$ The cost changes along with the number of binders purchased, and so the two proportions are equivalent. $\dfrac{2}{14} = \dfrac{\$3.46}{x}$